A techno-economical analysis of a CO2 heat pump

Abstract

There is a global concern for the environment and the impact we as humans have on it. The latest movement in the refrigeration sector is to phase out refrigerants such as Freons that contribute to global warming. This resulted in the industry being forced to start implementing natural refrigerants again. One solution identified is to use carbon dioxide (C02), CO2 is a natural gas found in the atmosphere, it has no ozone depleting potential and has a global warming potential of one. It is regarded as a safe gas seeing that it is non-flammable and nontoxic. The biggest challenge when using CO2 as a refrigerant in water heating heat pumps is the fact that it will work in a high pressure trans critical state. The advantage on the other hand is that the use of a gas cooler makes it possible to heat water to much higher temperatures than with conventional refrigerants. A techno-economical comparison was conducted between a water heating heat pump using CO2 as refrigerant arid another using R-22 as refrigerant. The comparison was based on simulated models of the mentioned heat pump systems. On comparison it was found that the CO2 heat pump has on average a 15% better COP than for R-22. This results in a 9.4% improvement in energy use for a complete hot water system using a CO2 heat pump rather than a conventional R-22 heat pump. From the results found it can be concluded that a CO2 heat pump system is a feasible possibility to replace HFC and HCFC refrigerants. It offers an environmentally friendly and energy efficient system for water heating in the domestic and commercial market. The outcome of this study forms the basis for future research and development on CO2 water heating heat pump technology at the North-West University.